> On Sun, 30 May 2010 13:04:10 -0700> mark gross <640e9920@gmail.com> wrote:> > > Low Power Events is a possible alternative to suspend blocker / wake> > lock API used by Android.> > Here is how I see your proposal. It is of course possible that I> misunderstood bits, so please correct me where I'm wrong.> > 1/ You have introduced a new mechanism for requesting a transition> to a low power state. This involves writing a number to /dev/lpe_enter.> It is not clear to me from your text what the magic number really means.> I think this parallels writing to /sys/power/state, but achieves the same> result though a different mechanism and adds some extra checking.> So: I don't understand the numbers, and I don't see why we need a> second way to request a low power state. Probably I missed something> important.

I can only think for lpe to provide the levels and have userspace andplatform code hook into there. Else you would have a dependency fromuserspace to platform code.

> > 2/ Rather than tracking wake-events from the hardware up through possibly> several kernel modules, you go directly from hardware to user-space so each> event is potentially presented to user-space twice: once as a "wake up> from low power state" event and once following the normal path (maybe a> key-press event, maybe a serial-port event, maybe a network receive event).> I can see that this is a very tempting approach. It allows all those> intermediate modules to remain unchanged and that is good.> However it isn't clear to me that this would be easy for user-space to use> correctly.> When an lpe event arrived it would need to wait around for the real event> to arrive and then process that. I probably wouldn't wait long, but it> would be an indeterminate wait, and it might not be trivial to determine> if all events that would cause a wake-up have been consumed as a direct> mapping from lpe event to normal event may not always be possible.> Maybe this is more of a theoretical problem and in practice it would be> easy to get it right - I don't have enough concrete experience to be sure.> > So: I like the idea of leaving the intermediate layers unchanged, but I'm> not convinced it would work.

To add to this: Is it a correct assumptionthat all wake-up events that leave a driver trickle eventually up touserspace?

I think splitting the actual driver product (i.e. keypress or whatever)of a wake-up-event and it's corresponding wake-lock is not possible.Because you would have to _somehow_ map the block back to the productwhen you consume the product.

If you want to abstract the blocking from the kernel-code you probablyhave to introduce an abstract "driver-product" entity where you can doall your blocking associated with the product but hidden from the codethat uses the product. (Which I don't think is feasible, because itincreases overhead)